Q: What DizonaBody.esp does? Why morphs are conflicting?! Why Dizona Body has so much conflicts?! Why beastraces have so much bugs?
A: By default, only the malehead.nif file is replaced in DB: it contains shader settings and texture paths.
DB by default doesn't have files that are responsible for emotions and morphs, i.e. DB does not affect them.
Skyrim will use morphs you already have installed in your game. Morphs are present in HighPoly Dizona Head, through (because morphs should be high-poly too)
As for esp and esm files, both are same, the only difference is in their priority. These files change the following:
human Skin (just changes the paths to body textures),
texture set of Age40 (new normal maps for the "old" textures) and male woodelf,
gives beastraces NPS duplicates of vanilla clothes, makes beastraces unplayable.
That's more or less all it does.